# std::ranges::borrowed_iterator_t, std::ranges::borrowed_subrange_t

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< cpp‎ | ranges

Defined in header `<ranges>` |  |
template< ranges::range R > using borrowed_iterator_t = /* see below */; | (1) | (since C++20)
template< ranges::range R > using borrowed_subrange_t = /* see below */; | (2) | (since C++20)

1) std::ranges::iterator_t<R> if `R` models `borrowed_range`, std::ranges::dangling otherwise.
2) std::ranges::subrange<std::ranges::iterator_t<R>> if `R` models `borrowed_range`, std::ranges::dangling otherwise.

These two alias templates are used by some constrained algorithms to avoid returning potentially dangling iterators or views.

### Possible implementation

borrowed_iterator_t
    template< std::ranges::range R >
    using borrowed_iterator_t = std::conditional_t<std::ranges::borrowed_range<R>,
        std::ranges::iterator_t<R>, std::ranges::dangling>;
borrowed_subrange_t
    template< std::ranges::range R >
    using borrowed_subrange_t = std::conditional_t<std::ranges::borrowed_range<R>,
        std::ranges::subrange<std::ranges::iterator_t<R>>, std::ranges::dangling>;

### See also

ranges::dangling (C++20) | a placeholder type indicating that an iterator or a `subrange` should not be returned since it would be dangling (class)

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